Catalyst and process for the conversion of methanol to acetaldehyde

Abstract

A catalyst mixture is made with improved activity and selectivity to acetaldehyde by using an inert diluent and specifically defined concentrations of cobalt, a halide, a trivalent phosphorus compound, and the inert diluent. Use of the trivalent phosphorus compound significantly inhibits corrosion of the reactor metal.

What is claimed is: 
     
       1. A catalyst system for the production of acetaldehyde by the reaction of methanol, carbon monoxide and hydrogen, which catalyst comprises (I) a source of cobalt, (II) a source of iodide or bromide, (III) an inert oxygen-containing diluent, and (IV) a trivalent phosphorus compound of the formula: ##STR2## wherein each R group taken individually is similar or different, and is; (a) a saturated or unsaturated, linear or branched alkyl group having from 1 to 20 carbon atoms, or (b) an aryl, aralkyl, or alkaryl group having from 6 to 10 ring carbon atoms, or (c) a saturated or unsaturated cycloalkyl having from 5 to 8 ring carbon atoms, or (d) when two such R groups are attached to the same phosphorus atom and taken together, a saturated or unsaturated divalent alkyl group having from 4 to 10 carbon atoms; and wherein n is an integer from 2 to 10, and wherein the inert diluent to methanol volume ratio is from 0.3:1 to 20:1, the cobalt concentration is from 1 to 40 milligram-atoms of cobalt per gram-mole of methanol charged, the halide to cobalt milligram-atom ratio is from 1:1 to 10:1; and the phosphorus to halide milligram-atom ratio is from 0.1:1 to 2.8:1. 
     
     
       2. The catalyst of claim 1 wherein each R group taken individually is similar or different, and is; (a) a saturated or unsaturated, linear or branched alkyl group having from 4 to 10 carbon atoms (b) an aryl, aralkyl, or alkaryl group having 6 ring carbon atoms, or (c) a saturated or unsaturated cycloalkyl having from 5 to 6 ring carbon atoms, or, (d) when two such R groups are attached to the same phosphorus atom and taken together, a saturated or unsaturated divalent alkylene group having from 4 to 10 carbon atoms; and wherein n is an integer from 2 to 6. 
     
     
       3. The catalyst of claim 1 wherein the diluent to methanol volume ratio is from 0.5:1 to 8.1, the cobalt concentration is from 3 to 15 milligram-atoms of cobalt per mole of methanol charged, the iodide or bromide to cobalt milligram-atom ratio is from 2:1 to 10:1, and the phosphorus to halide milligram-atom ratio is from 0.4:1 to 2:1. 
     
     
       4. The catalyst of claim 3 wherein the iodide or bromide to cobalt milligram-atom ratio is from 2:1 to 6:1. 
     
     
       5. The catalyst of claim 1 wherein the trivalent phosphorus compound is triphenylphosphine. 
     
     
       6. The catalyst of claim 1 wherein the trivalent phosphorus compound is tricyclohexylphosphine. 
     
     
       7. A process for the production of acetaldehyde by the reaction of methanol, carbon monoxide and hydrogen wherein the reaction is catalyzed by cobalt and an iodide or bromide promoter in the presence of an inert oxygen-containing diluent and a trivalent phosphorus compound of the formula: ##STR3## wherein each R group taken individually is similar or different, and is; (a) a saturated or unsaturated, linear or branched alkyl group having from 1 to 20 carbon atoms, (b) an aryl, aralkyl, or alkaryl group having from 6 to 10 ring carbon atoms, or (c) a saturated or unsaturated cycloalkyl having from 5 to 8 ring carbon atoms, or (d), when two such R groups are attached to the same phorphorus atom and taken together a saturated or unsaturated divalent alkylene group having from 4 to 10 carbon atoms; and wherein n is an integer from 2 to 10, the diluent to methanol volume ratio is from 0.3:1, to 20:1, the cobalt concentration is from 1 to 40 milligram-atoms of cobalt per gram-mole of methanol charged, the halide to cobalt milligram-atom ratio is from 1:1 to 10:1, and the phosphorus to halide milligram-atom ratio is from 0.1:1 to 2.8:1, the hydrogen to carbon monoxide mole ratio is from 0.2:1 to 10.1. 
     
     
       8. The process of claim 7 wherein each R group taken individually is similar or different, and is a (a) a saturated or unsaturated, linear or branched alkyl group having from 4 to 10 carbon atoms (b) an aryl, aralkyl, or alkaryl group having 6 ring carbon atoms, or (c) a saturated or unsaturated cycloalkyl having from 5 to 6 carbon atoms, or (d), when two such R groups are attached to the same phosphorus atom and taken together, a saturated or unsaturated divalent alkylene group having from 4 to 10 carbon atoms; and wherein n is an integer from 2 to 6. 
     
     
       9. The process of claim 7 wherein the diluent to methanol volume ratio is from 0.5:1 to 8.1 cobalt concentration is from 3 to 15 milligram-atoms of cobalt per gram-mole of methanol charged, the iodide or bromide to cobalt milligram-atom ratio is from 2:1 to 10:1 the phosphorus to halide milligram-atom ratio is from 0.4:1 to 2:1. 
     
     
       10. The process of claim 9 wherein the iodide or bromide to cobalt milligram-atom ratio is from 2:1 to 6:1. 
     
     
       11. The process of claim 7 wherein the trivalent phosphorus compound is triphenylphosphine. 
     
     
       12. The process of claim 7 wherein the trivalent phosphorus compound is tricyclohexylphosphine. 
     
     
       13. The process of claim 7 wherein the hydrogen to carbon monoxide mole ratio is from 0.2:1 to 10:1, the temperature is 120° C. to 250° C. and the pressure is from 1,000 psig to 10,000 psig. 
     
     
       14. The process of claim 13 wherein the hydrogen to carbon monoxide mole ratio is from 0.25:1 to 5:1, the temperature is from 160° C. to 225° C. and the pressure is from 1,500 psig to 6,000 psig. 
     
     
       15. The process of claim 14 wherein the hydrogen to carbon monoxide mole ratio is from 0.5:1 to 1.5:1.